An active matrix organic light-emitting diode (AMOLED) display has currently become a hotspot in the research field of a flat-panel display. As compared with a liquid crystal display (LCD), the OLED display has such advantages as low power consumption, low production cost, self-luminescence, a wide viewing angle and rapid response. Recently, the OLED display has replaced with the traditional LCD in mobile phones, personal digital assistants (PDAs) and digital cameras. The design of a pixel driving circuit, as a core technique for the AMOLED display, is of very important significance.
Different from a thin film transistor LCD (TFT-LCD) where the brightness is controlled through a stable voltage, the OLED display is driven by a current, and it is required to control the light emission through a stable current. Due to the limitations of a manufacture process and the aging of elements, a threshold voltage (Vth) of a driving TFT for each pixel will be drifted, which thus result in a change of the current flowing through the OLED of each pixel along with the threshold voltage. As a result, uneven display brightness will occur and a display effect of an entire image will be adversely affected.
Recently, an in-cell touch technique has been successfully applied in the LCD, so as to provide a thin LCD display and improve the integration thereof. Hence, the integration of the in-cell touch technique with the AMOLED will certainly become a new trend of the display device.